This invention relates generally to inkjet printers, and more particularly to sensing when the ink has run out of one or more of the inkjet cartridges of such printers.
Inkjet printers have become increasingly inexpensive and increasingly popular, especially for home computer users. A typical inkjet printer usually has a number of common components, regardless of its brand, speed, and so on. There is a print head that contains a series of nozzles used to spray drops of ink onto paper. Ink cartridges, either integrated into the print head or separate therefrom, supply the ink. There may be separate black and color cartridges, color and black in a single cartridge, a cartridge for each ink color, or a combination of different colored inks in a given cartridge. A print head motor typically moves the print head assembly back and forth horizontally, or laterally, across the paper, where a belt or cable is used to attach the assembly to the motor. Other types of printer technologies use either a drum that spins the paper around, or mechanisms that move the paper rather than the print head. The result is the same, in that the print head is effectively swept across the paper linearly to deposit ink on the paper. Rollers pull paper from a tray, feeder, or the user""s manual input, and advance the paper to new vertical locations on the paper.
Inkjet printers have advanced to the point where they can now be used to print high-quality prints from photographic images taken by digital cameras, scanned in from conventional prints, or synthetically generated images, such as animated images. Since digital cameras have also become increasingly inexpensive and popular, many users opt to take digital pictures and print them on inkjet printers, instead of taking pictures on regular film and having them professionally developed. With commonly available computer software, users have the ability to crop, remove redeye, and perform other modifications to the pictures prior to printing them on their printers. The combination of a digital camera and an inkjet printer allows a home user to have significantly more control over the photographic printing process than if the user were to take pictures with a regular camera and have them professionally developed.
A downside to printing photographic images and other high-quality color images and documents on an inkjet printer, however, is that both replacement ink cartridges and the special inkjet paper used to obtain optimal prints can be expensive. Many users may opt to print draft-quality images on less-expensive or non-inkjet paper before printing their final prints. Furthermore, most affordable inkjet printers print quite slowly at their highest-quality settings. When a user wants to print thirty, forty, or more standard-size four inch-by-six inch prints on such an inkjet printer, he or she is likely to start the print job before going to sleep at night or going to work in the morning. When the user wakes up or comes home from work, the job will by then have finished. This technology has also been extended to fax printing, or any printing that is either unattended, such as faxes are, or takes a long time to print, such as printing photos, or printing large-format computer-aided design (CAD) drawings.
A difficulty with this approach, however, is that one or more of the color or black inks may run out while the printer is printing. In a best-case scenario, the printer may detect the ink running out, and abort printing to avoid wasting expensive inkjet paper. If the printer were to continue printing, paper would be wasted because typically only one of the commonly found three, four, or six ink cartridges runs out of ink. Therefore, ink is still deposited on the paper, but not in the right color combinations according to the image being printed. In a worst-case scenario, the inkjet printer may not detect the ink running out until many sheets of the expensive inkjet paper have been ruined, at potentially considerable cost and frustration to the user. This may occur even if the printer is equipped with an ink-out sensing capability, especially for printers having foam ink cartridges.
Foam ink cartridges have foam within the cartridge to store the ink. The foam generally enables the inkjet printer to print more refined and smaller droplets of ink than non-foam ink cartridges, as well as providing other advantages. However, a disadvantage to using foam is that ink tends to pool in the lowest section of the foam, especially during inter-sheet delays. Inter-sheet delays result from the already printed sheet being ejected out of the printer, a new sheet being fed into the printer, and inkjet print head calibration and other processes being performed prior to the printer printing on the new sheet. Printers equipped with ink-out sensing capability typically check for a low- or no-ink condition just prior to a new sheet being printed, after the inter-sheet delays have been incurred. However, because the ink collects in the lowest section of the foam in the cartridge, this verification will erroneously pass, indicating that there is ink in the cartridge, when in fact there is not sufficient ink to print a complete image on the new sheet that has been fed into the printer.
FIG. 1 depicts in a diagrammatical manner this overall process 100 according to the prior art. A number of sheets 102A, 102B, . . . , 102N are to be printed on by the inkjet printer. Ink checks 104A, 104B, . . . , 104N are performed before the printer begins printing on the corresponding sheets 102A, 102B, . . . , 102N. There may be sufficient ink in the ink cartridges to print the first sheet 102A. Therefore, the ink check 104A yields an OK status, and the sheet 102A prints acceptably. However, by the end of the printing of the sheet 102A, the ink stored in one of the ink cartridges may have sufficiently depleted so that printing the second sheet 102B results in a ruined, unacceptable image. The ink check 104B still yields an OK status, because there is still ink in this cartridge.
For subsequent sheets, such as the sheet 102N, the ink checks, such as the ink check 104N, should yield a rejected status, indicating that the ink has run out or is otherwise very low, such that images are not printed on these sheets, and printing aborts. However, because ink pools in the bottom of the foam of the cartridges, the ink check still yields an OK status, even though the ink has essentially run out. The printer thus still prints on the sheet 102N, because the ink check 104N yields an OK status, even though there is insufficient ink in one of the cartridges. Rather than only one expensive sheet being ruined, the sheet 102B, the sheets through the sheet 102N are also ruined, due to the inability of the inkjet printer to recognize that ink is pooling in the bottom of the foam of the cartridge during inter-sheet delays. If the user is not monitoring the progress of the print job, as is typically the case where a large number of sheets are being printed, this causes a large number of sheets to be ruined.
For these and other reasons, therefore, there is a need for the present invention.
The invention relates to sensing out-of-ink conditions for an inkjet printer while the printer is printing. A method of the invention includes performing the following at least once during printing on a sheet by an inkjet printer. First, the buffer color information for a swath to be printed next on the sheet by the printer is evaluated. The printed color information for the swath is then measured as the swath is printed on the sheet. If the printer color information is less than substantially equal to the buffer color information, one or more out-of-ink actions, such as notifying the user, aborting printing, and so on, are performed.
A printer of the invention includes one or more sources of ink, an inkjet print head, a swath buffer, a sensor, and an out-of-ink mechanism. The print head prints ink from the sources of ink onto a sheet of paper. The buffer stores buffer color information for a swath to be printed next on the sheet by the print head. The sensor determines printed color information for the swath as printed on the sheet. The mechanism performs one or more out-of-ink actions in response to determining that the printed color information is less than substantially equal to the buffer color information.
A computer-readable medium of the invention has instructions stored thereon for execution by a processor to perform a method. The method includes performing the following at least once during printing on a sheet by an inkjet printer. First, a buffer amount of each ink color to be printed next on the sheet is determined, as well as the actual amount of each ink color printed. If the actual amount of any ink color printed on the sheet is less than substantially equal to the buffer amount of the ink color, one or more out-of-ink actions are performed.
Embodiments of the invention provide for advantages over the prior art. The comparison of buffer color information to printed color information can be performed periodically or even continuously while the inkjet printer is printing. This means that an ink-out condition is likely to be nearly immediately detected, such that printing can be aborted without ruining any sheets other than the current sheet. Ink is also saved, since the printing does not continue, which is especially significant in multi-cartridge printers. Because the ink level is checked while the printer is printing, the ink does not have a chance to collect at the bottom of the foam in the cartridge, so that erroneous acceptable ink-level checks are avoided. Still other advantages, embodiments, and aspects of the invention will become apparent by reading the detailed description that follows, and by referring to the accompanying drawings.